JPS5835540B2 - aromatic polyamide dope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an isotropic dope made of a substituted aromatic polyamide with P (para) orientation, which is advantageous both physically and industrially.

Conventionally, it is already known that halides of lithium chloride, calcium chloride, and other alkali metals and alkaline earth metals are added to solubilize P-oriented aromatic polyamides in organic solvents. In particular, when lithium chloride or calcium chloride is used as a dissolved salt for P-oriented polymers, the polymer becomes an optically anisotropic dope during organic solvent dissolution, and such anisotropic dopes have high strength and high elastic modulus. It is known that the fibers have excellent anisotropy.

However, such anisotropic fibers are merely rigid, and it is difficult to draw them after that.And even if one tries to form a film from such anisotropic dope, it is simply cast. Even if the shearing during casting causes orientation of the polymer chains, only a very weak product can be obtained in the direction perpendicular to the casting direction.

Of course, such films cannot be stretched biaxially or even uniaxially.

Such an orientation tendency has the disadvantage that it cannot be suppressed even by static heating after casting.

In particular, unlike fibers, films require balanced strength not only in one direction but in all directions within the same plane, and such films cannot be made from conventional optically anisotropic aromatic polyamide dope. It was difficult to obtain.

The present invention aims to improve the drawbacks of such an optically anisotropic dope and provide an isotropic dope of P-oriented substituted aromatic polyamide which is advantageous both physically and industrially.

That is, the present invention is based on the general formula (where X and Y are selected from C1 to C3 alkyl, alkoxy, nitrohalogen, and cyan group, and n
, m represents an integer from O to 4, but cannot be O at the same time)
a substituted aromatic polyamide with an intrinsic viscosity of 1.5 or more containing as a main structural unit, at least one solvent selected from N-methylpyrrolidone and N,N'-dimethylacetamide, and lithium bromide or/and calcium bromide. It is a substituted aromatic polyamide isotropic dope consisting of.

The dope of the present invention is optically isotropic, and this property was only achieved when the above-mentioned polymer, solvent, and inorganic salt were specified.

This property has the characteristic that it does not change in any range of polymer concentration from 1.0 to 70 wt% and inorganic salt concentration from 10 to 200 wt% (based on the polymer).

The polymer used in the present invention is a p-oriented substituted aromatic polyamide whose main constituent unit is (70゛Φ゛'') OXn OYm (where X,
Y is C1-C3 alkyl, C1-C3 alkoxy,
selected from nitro halogen, cyano group,
n and m represent integers from O to 4, but cannot be O at the same time).

For example, structural units having the following structures can be exemplified.

It is desirable that the main structural unit is contained in an amount of 70 mol % or more from the viewpoint of the strength and elastic modulus of the film.

Further, the nuclear substituent in the above general formula has the effect of solubilizing the polymer in an organic solvent, and also has the effect of improving properties such as hygroscopicity in the final molded product.

In addition, if the amount is less than 30 mol%, it may contain bonds other than amide bonds (for example, bonds of ester, imide, urethane, ether, etc.) and soft bond units such as m (meta) bonds even if they are amide bonds. I can't help it.

However, the effect of the doping of the present invention, which is isotropic and has good film-forming properties, is most noticeable when the main structural unit is 9
This is the case of 0 to 100 mol%.

Among the main components of the present invention, a particularly preferred polymer structure is a substituted aromatic polyamide having an asymmetrical chlorine atom, for example, the following structure as a main component.

The soluble inorganic salts used in the present invention are also specified as lithium bromide and calcium bromide.

Other halogenated inorganic salts such as lithium chloride, calcium chloride, magnesium bromide, and strontium bromide cannot be used because they have disadvantages such as making the dope anisotropic and causing polymer precipitation over a wide area. The N-substituted amide solvent used in the invention is N-
It must be at least one solvent selected from methylpyrrolidone and N,N'-dimethylacetamide.

N-methylpyrrolidone is generally N-methy/L/-
2-pyrrolidone is used.

Solvents other than those mentioned above make it difficult to dissolve the substituted polyamide of the present invention, making it impossible to obtain an isotropic dope.

Next, the dope of the present invention will be explained.

The dope of the present invention is an optically isotropic composition composed of the above-mentioned three specific components, but when forming, for example, a film from such a dope, further Products with excellent physical properties can be obtained.

That is, the intrinsic viscosity (η1nh) of the polymer used in the present invention needs to be 1.5 or more when measured at 30° C. in concentrated sulfuric acid under the condition of 0.5 g/100 ml.

As a result, molded products such as films with high strength cannot be obtained from dopes using polymers with low intrinsic viscosity.

Also, the appropriate amount of lithium bromide and/or calcium bromide to be used in the dope is 10 to 200 wt% based on the weight of the polymer, but considering the desalting time during film formation and the precipitation of the polymer from the dope, it is 15 to 200 wt%. Most preferably 200 wt%, more preferably 30 to 100%.

Furthermore, the polymer concentration in the total dope is 1.0 to 70w.
It can be used within the range of 1 t%, but taking into account film productivity, system viscosity, etc., it is preferable to use a polymer concentration of 3 to 70 wt%, and higher than 6 wt% for films with excellent physical properties. , especially higher than 6 wt% < 2
Up to 0 wt% is preferred.

It is preferable that the dope of the present invention satisfies at least one of the above-mentioned conditions, and this condition can be applied as it is to the production of molded products other than films, such as fibers and other molded products.

Since the dope of the present invention has the advantage of excellent stretching properties, it can be applied to any molding process, and molded products can be manufactured in the usual manner.

Generally, a rotational viscometer is used as a simple method to measure the viscosity of dope, but it can also be measured using a rheometer or a high-performance flow tester.

First, a change in viscosity of the optically isotropic dope of the present invention is measured using a rotational viscometer.

If we plot this change with the logarithm of the viscosity on the vertical axis and the temperature on the horizontal axis, we can see that the viscosity changes linearly to lower values as the temperature increases (from -50'C to the boiling point of the solvent), and the viscosity change is plotted against the polymer concentration. When plotted, the viscosity change expressed in logarithm increases linearly as the concentration becomes higher (1 to 70 wt%).

On the other hand, when a conventional optically anisotropic dope is measured in the same manner as described above, a sharp discontinuity point (the viscosity becomes undefined) occurs in the middle of the measurement in any case.

Also, when measuring the viscosity with a rotational viscometer by changing the rotational speed of the rotor, there is no significant change in isotropic dope, but with anisotropic dope, the apparent viscosity decreases as the rotational speed increases. For example, 5200 cp at 1 rpm
However, when the speed is increased to 5 rpm, the difference becomes more than double, showing 1700 cp.

As described above, the properties of the p-oriented aromatic polyamide dope differ significantly depending on whether it is optically isotropic or anisotropic.

Such differences greatly affect the production of molded products and the properties of molded products.

For example, when an anisotropic dope is supplied to a film forming process, the apparent viscosity varies greatly due to shearing inside the die or screw extruder during film forming, which tends to cause uneven film discharge and uneven film thickness. As mentioned above, the resulting film is extremely weak and opaque in the direction perpendicular to the discharge direction, and cannot be stretched.

On the other hand, the isotropic dope of the present invention can be supplied to a normal film forming process without worrying about such problems, and can produce a uniform and smooth film, as well as the strength required for the film. It has the great advantage that it has sufficient transparency and can be subjected to subsequent stretching processing.

Further investigation revealed that there is a large difference in the refractive index of the film, that is, the difference between the high refractive index in either the vertical or horizontal direction and the refractive index in the thickness direction is usually 0.3 or less for the film made of the dope of the present invention. (at most 0.4), whereas those made of anisotropic dope have a difference of 0.6 or more, and in the case of fibers (axial refractive index - diametrical refractive index), the former is 0. The latter has a difference of 0.7 or more compared to .6 or less.

Therefore, by measuring the refractive index, it is possible to determine from the molded article which dope it is made of.

A simple way to determine whether a dope is isotropic or anisotropic is that an anisotropic dope exhibits birefringence when observed with an optical polarization microscope, and an anisotropic dope exhibits birefringence when a slight shear is applied to the dope. It exhibits luster, but isotropic doping exhibits neither such birefringence nor luster.

Furthermore, it can be easily distinguished from the fact that anisotropic dope is opaque while isotropic dope is transparent.

The polymer used in the present invention is produced by homo-solution polymerization of diacid halide and diamine in a specific N-substituted amide solvent containing a soluble inorganic salt, or contains no inorganic salt or even if it does contain a small amount. It can be obtained by polymerization by conventional methods such as precipitation or swelling polymerization in a small amount of solvent, so-called interfacial polymerization, or by neutralization with a base or the like.

To prepare a dope, homogeneous solution polymerization in an N-substituted amide solvent containing the inorganic salt is easy. It can also be adjusted by redissolving it.

In the polymerization of acid halides and diamines, inorganic bases such as calcium hydroxide, lithium carbonate, calcium oxide, and calcium hydride can be used to neutralize the generated hydrogen halide. Although halides are produced, these neutralized products may be mixed into the dope of the present invention as long as the amount is equivalent to neutralization.

In addition, if these neutralized salts are present, salt recovery during membrane formation becomes complicated and undesirable, it is preferable to redissolve the previously isolated polymer in a solvent system containing only the inorganic salts.

The dope of the present invention may contain small amounts of additives such as ultraviolet absorbers and antistatic agents. It is convenient.

In other words, after casting the dope onto a support, part of the solvent is evaporated and the dope is concentrated, and then the film is peeled off, or the wet-dry method is used in which the support is introduced into an aqueous bath, or the dope is directly introduced in the form of a film into an aqueous medium. This is a wet method.

In this case, the aqueous medium used must be one that can extract the inorganic salts and residual solvents in the dope, and generally an aqueous medium is used, but alcohols such as ethylene glycol and solvents contained in the original dope must be used. It may also contain other water-soluble solvents, surfactants, etc.

The film that has gone through the wet process in this way is devolatilized under reduced pressure or under heat, and can be made into a final film.

During this process, the film can be stretched uniaxially or biaxially in the longitudinal or transverse direction of the film.

In general, polyamides have a drawback of high moisture absorption and large dimensional changes due to moisture absorption, but this moisture absorption can be reduced by improving the degree of crystallinity.

The film made from the polymer of the present invention can also be heated to lower its moisture absorption rate and improve other physical properties.

Molded products manufactured from the dope of the present invention have excellent smoothness and well-balanced physical properties.For example, the film has excellent transparency and is required to have heat resistance and electrical insulation properties. It is effective for various uses and applied technologies such as base films for magnetic tapes and base films for condenser diaphragms.

The present invention will be explained below with reference to examples.

Example 1 and Comparative Example 1 2.51 parts of dehydrated N-methylpyrrolidone to 1 part of 2-chloro-p-phenylenediamine in a 51-volume tabletop kneader.
After dissolving 42.60 g (1 mol), 203.03 g (1 mol) of solid terephthalic acid chloride was added and 10
Stirred at ~20°C for 2 hours.

The system is initially uniform and transparent, but gradually becomes cloudy and the polymer begins to precipitate in a swollen state.

This system was put into a mixer filled with water, the polymer was reprecipitated, washed with water and acetone repeatedly, and dried under reduced pressure.
Poly-2-chloro-p-phenylene terephthalamide was obtained exhibiting inb = 5.79.

ηinb is polymer 5 g/l 0 using concentrated sulfuric acid as a solvent.
Measurements were made using an Uberote viscometer at 30°C at a concentration of 0-.

The isotropic doped polymer of the present invention was added to a solvent containing hexamethylphosphoramide, N-methylpyrrolidone and lithium bromide in a ratio of 2:1:0.04 (weight ratio) so that the polymer concentration was 4%. dissolved in.

The system was completely uniform, pale yellow and transparent, and even when observed under a polarizing microscope, it was completely isotropically doped.

Polymer was added to a solvent containing anisotropically doped hexamethylphosphoramide, N-methylpyrrolidone, and lithium chloride in a ratio of 2:1:0.04 (weight ratio) so that the polymer concentration was 4%. 2-Chlo/I/-p-phenylene terephthalamide was dissolved.

The system was grayish-white and opaque, and showed metallic luster with slight shearing. It also showed birefringence under a polarizing microscope, and it was confirmed that it formed an optically anisotropic dope.

The viscosity was measured using a B5 type rotational viscometer (Toyo Keiki Seisakusho) using rotor/167.

The isotropic dope according to the present invention has a linear relationship between the logarithm of the viscosity and the temperature, but the anisotropic dope shows a discontinuous peak around 105°C and the viscosity varies considerably depending on the rotation speed of the viscometer. There was found.

Formation of a film from the dope of the present invention After casting the dope of the present invention onto a glass plate, it was immersed in water at room temperature for 10 minutes to desalinate and remove the solvent, and then fixed on a frame and heated at 300°C for 3 minutes. A transparent uniform film with a thickness of 5 μm was obtained.

This film has a strength of 9/nmf at 40, 97 nmf at 41, an elongation of 25%, an elongation of 23%, 9/mtii at 1200,
It had an initial elastic modulus of 1250 to 9/-.

Formation of film from anisotropic dope The anisotropic dope containing lithium chloride was similarly cast onto a glass plate, and then immersed in water for 10 minutes.

At this stage, the film was gray and opaque, the film was weak in the direction perpendicular to the casting direction, and was highly susceptible to tearing in the casting direction.

When this film was fixed to a frame and heated at 300° C. for 3 minutes, a film-like material with an average diameter of 7 μm was obtained, but it was gray and opaque with cracks in the casting direction in some places.

This material had a strength of 23 kg/rriA in the casting direction, an elongation of 2%, and an initial elastic modulus of 1100 of 9/-.
The strength and elongation and elastic modulus could not be measured because it was too weak in the perpendicular direction.

In this way, it has been found that a film having practical physical properties in both orthogonal directions cannot be made from anisotropic doping.

Example 2 and Comparative Example 2 Similar polymerization was carried out using the same solvent and monomer as in Example 1, but 0.99 mol (201,00 g) of terephthalic acid chloride was used to obtain a polymer with low ηinb. Poly-2-chloro-p-phenylene terephthalamide having ηinh = 1.60 was obtained.

This polymer was mixed with 2 parts of hexamethylphosphoramide, 1 part of N-methylpyrrolidone, and 0.1 part of lithium bromide (weight ratio).
An isotropic dope was obtained by dissolving the polymer in a solvent containing 5% to 15%.

Separately, this polymer was dissolved in a solvent containing 2 parts of hexamethylphosphoramide, 1 part of N-methylpyrrolidone, and 0.1 part of lithium chloride (by weight) within a similar concentration range.
It was confirmed that an anisotropic phase was formed in a region where the polymer concentration was 10% or more.

Example 3 250ml of dried dimethylacetamide was placed in a 500rrL flask, and 4.86ml of p-phenylenediamine was added.
6g and 0.765 2-nitro-p-phenylenediamine
7g Calcium bromide 7,000g dissolved in water bath 0~
Cool to 5°C.

Into this, liquid 2-chloroterephthalic acid chloride 11
．． After adding 874 g and stirring for about 1.5 hours, the contents gradually become viscous while remaining uniformly transparent.

Further, 3.705 g of calcium hydroxide was added to neutralize hydrogen chloride generated in the system, and stirring was continued for an additional hour at room temperature.

The ηinb of the polymer was 3.50 in sulfuric acid. The obtained dope had a polymer concentration of 5.3% and was heated from -20°C to 160°C.
It is optically isotropic between 0.degree. and no discontinuities in plots of temperature or concentration (as varied by dilution or concentration) versus viscosity.

After casting this dope onto a glass plate, it was left in an oven at 100°C for 10 minutes to scatter some of the solvent, and then immersed in an aqueous bath containing 10% dimethylacetamide at 80°C for 5 minutes. The film was washed under running water, fixed on a frame, and dried at 80° C. under reduced pressure using a vacuum pump for 24 hours.

Furthermore, the film was heated to 400°C with the film fixed to the frame.
The mixture was heated for 10 seconds to obtain a pale yellow transparent 10μ film.

This film has strength, elongation, and
Young's modulus is 30, 9/moli, 15%, 990k, respectively.
It was a uniform film with y/self and 25 kg/rmA, 17%, 920 and 9/mA.

On the other hand, if this polymerization is carried out in a salt other than bromide such as calcium chloride or lithium chloride, a polymer with ηinh > 3.0 will be produced, and at higher concentrations the dope will become opaque during polymerization and exhibit anisotropy. It will be like that.

Comparative Example 3 This example shows an example in which a concentrated sulfuric acid solution of a p-oriented aromatic polyamide subjected to nuclear thermal displacement is not suitable for film formation.

A mixed solvent 31 consisting of 2 parts of dehydrated hexamethylphosphoramide and 1 part of N-methylpyrrolidone (weight ratio) was put into a kneader of 142.p-phenylenediamine.
Dissolves 59g+! : Stir at 5°C.

Powdered terephthalic acid chloride 203.03g into this
When added, the system gradually increases in viscosity, but soon polymer precipitation begins and the system becomes powder-like.

After stirring for about 2 hours, the contents were poured into a large amount of water containing sodium carbonate to reprecipitate the polymer.

The recovered polymer is washed with water and acetone and dried under reduced pressure.

The poly-p-phenylene terephthalamide obtained exhibited an η inb of 4.95 in sulfuric acid.

Add this polymer to 98% concentrated sulfuric acid to a concentration of 12%.
When remelted at 0 to 90° C., the system was uniformly dissolved but exhibited metallic luster, and exhibited anisotropy such as birefringence under illumination.

This dope was cast onto a glass plate that had also been heated to about 80°C while being kept at about 80°C, and after being left as it was for about 3 minutes, it was poured into a 50% sulfuric acid aqueous solution cooled to 0°C.
I left it in running water at room temperature for 5 minutes to remove the flow, but the result was only a split yarn-like opaque material that could be torn in the casting direction with a slight force, but no practical film could be obtained. Ta.

Comparative Example 4 This example is a system that forms an anisotropic dope outside of the present invention, but when a film is produced in an isotropic region on the very low concentration side, the film formation rate is slow and the film formation is stable. It also shows that it is difficult.

The poly-2-chloro-p-phenylene terephthalamide obtained in Example 1 was added to a solvent containing hexamethylphosphoramide, N-methylpyrrolidone, and lithium chloride in a ratio of 2:1:0.04 (weight ratio). The polymer was dissolved to a concentration of 1.5%.

As shown in Comparative Example 1 above, in this system, the polymer concentration was 4.
%, it is already anisotropic, and in order to make it completely isotropic, the polymer concentration must be lower than 2%, which requires the use of a large amount of solvent.

The dope with a concentration of 1.5% thus obtained was uniformly cast onto a glass plate, immersed in water at room temperature for 10 minutes, and desalted.
Solvent removal was performed.

However, when trying to obtain a thin film, the strength of the film in water was weak, probably due to the low polymer concentration, and the film broke before being fixed to the frame.

Furthermore, when attempting to obtain a thick film of 20 μm or more, a phenomenon of devitrification of the film occurs, making it extremely difficult to obtain a uniformly transparent film.

On the other hand, this dope was spread on a glass plate in the same way.
Dry in an oven at ℃ for 10 minutes (If the dope of the present invention in Example 1 was used with a polymer concentration of 5% and the same drying was performed, it could be uniformly dried to a self-supporting state) However, the film was still not self-supporting, and after further heating at the same temperature for a total of 30 minutes, it finally became self-supporting, but some whitening due to polymer precipitation was observed, and dry process It was found that the process requires long drying time, which is not a desirable result from an industrial perspective.

Example 4 Polymer of Example 1 (ηinh = 5.79) A biaxially stretched film was produced using an isotropic dope consisting of tohexamethylphosphoramide, N-methylpyrrolidone, and lithium bromide.

First, the above dope was cast onto a glass plate, immersed in water at room temperature, and stretched 1.5 times in the longitudinal direction while being demineralized and desolvated for 10 minutes, and then stretched 1.5 times in the transverse direction. and heated at 300° C. for 3 minutes to obtain a transparent and uniform film with a thickness of 5 μm (Film A).

Another above-mentioned dope was used for casting, salting and desolvation in the same manner as in Example 1, and then the obtained film was heated at 300° C. for 3 minutes.

During this heating, the film was
．． A transparent film with a thickness of 5 μm was obtained by stretching 5 times (film B).

The physical properties of film A are strength (kL'mca) vertical 52,
Width 53, elongation (%) vertical 19.2, horizontal 176, initial elastic modulus (kg/nmi) vertical 1560, horizontal 1625
Met.

Film B was a transparent film having almost the same physical properties as Film A, although slightly lower.

Claims (1)

[Claims] 1 General formula - (where X and Y are C1 to C3 alkyl groups, C1 to C3
alkoxy group, nitro group, halogen group, and cyano group, and n and m represent integers from O to 4, but cannot be O at the same time), and have an intrinsic viscosity of 1.5 or more. An isotropic dope made of a substituted aromatic polyamide, comprising a substituted aromatic polyamide, at least one solvent selected from N-methylpyrrolidone and N,N'-dimethylacetamide, and lithium bromide or/and calcium bromide.